Electrical harnesses are produced by cutting insulated wire to the desired length, stripping insulation from the cut ends and then applying terminals to one or both of the cut ends. In the typical wire cutting and stripping process, wire contained on a supply coil is fed in predetermined increments of length by cooperating feed rolls or belts to a cutting and stripping station. The cutting and stripping station includes a pair of central cooperating cutting blades and two pair of cooperating stripping blades which are located in spaced relation on either side of the cutting blades. After the predetermined length of wire has been fed through the cutting and stripping station, the cutting and stripping blades are moved toward each other, causing the cutting blades to sever the wire and simultaneously causing the stripping blades to cut the insulation.
Wire gripping units, located both upstream and downstream from the cutting and stripping station, grip the wire as well as the cut length of wire, and move the wire and cut length in opposite directions, thereby stripping slugs of insulation from the ends of the wire and from the cut length.
In a typical wire feeding and measuring apparatus as described in U. S. Pat. No. 5,060,395, the wire is fed by a pair of cooperating endless feed belts, which engage opposite sides of the wire. The feed belts are intermittently driven by a servo motor which is programmed to drive the feed belts forwardly and feed a predetermined length of wire and then stop movement of the wire. As described in the above patent, a drive wheel is located downstream of the feed belts and a measuring wheel is located opposite the drive wheel. The measuring wheel rides against the wire and measures the actual distance the wire has moved and provides a feed-back signal through an encoder to a controller. In the event wire slippage occurred during forward feeding movement, the controller uses the feedback signal to ascertain whether less or more wire than the predetermined length has actually been fed, and commands the feed belts to feed the wire either forwardly or in reverse to correct for the discrepancy.
The wire feeding mechanism as described in the aforementioned patent is very accurate and repeatable when using a wire having a firmly bonded plastic insulation. Certain types of heat resistant insulated wire include an outer woven fabric-like covering, and it has been found that when this type of insulation is cut, the material will fray. Thus, with this type of insulated covering, the insulation is normally not cut by the stripping blades, but instead is subjected to a burning action in which cooperating heated dies engage the wire at spaced locations to burn short lengths of the insulation away from the wire, and provide two spaced areas of exposed bare wire. The burning operation will fuse the fibrous material adjacent the burned area, thereby preventing fraying.
Following the burning operation, the wire is moved in increments to the cutting and stripping station, and it is necessary to precisely align the cutting blades at the cutting and stripping station with the midpoint of the length of the insulation between the two burned areas and to align the stripping blades with the exposed bare wire areas. Due to the fact that the insulation is not bonded to the wire, but instead is loosely woven on the wire, and as several increments of movement are required in moving from the burning station to the cutting and stripping station, there is a possibility for cumulative error, such that the burned areas may not be precisely positioned with respect to the cutting and stripping units.
An electrical terminal is usually attached to the stripped end of the wire and/or to the stripped end of the cut length. The typical terminal includes an insulation crimp which is crimped about the insulation adjacent the stripped end, and a wire crimp which is crimped to the bare wire. A gap or window is located between the two crimps. In production it is important that the insulation shoulder, which borders the stripped wire end, be located within the window. If the burned areas in the insulation are not properly positioned with respect to the cutting and stripping blades, the stripped wire end may be of an improper length, which means that the shoulder on the insulation bordering the stripped end will not be aligned with the window in the terminal, making the terminal connection defective and necessitating the scrapping of the wire and connected terminal.